Yeah .... For the most part it's pretty easy. Its only complicated when you get units like the Kairic Acolytes. They have 4 different weapon options, one of which is 3 per 10 models. (but the 'unit champion' can technically take one)
also, in unrelated news - @Thairne - just finished reading Fallen Angels... very interesting background on the Dark Angels for certain... which book is the "calamitous events of the warp breach that destroyed most of Caliban" in??